73^ 



NATURE 



[August 12, 1920 



which has a magazine of paper lasting him a 

 week, and he is enabled to type four copies at 

 once by means of ribbons instead of carbon paper. 

 The blind man is trained by visualisation, and is 

 taught to use a cross-sectioned visualising board, 

 on which the tools and equipment he is using are 

 placed at fixed points. Thereby great waste of 

 time and effort is saved. The importance of find- 

 ing work that cripples can do, and of teaching 

 them to do the work, is insisted on. Not only 

 have the war cripples to be considered, but also 

 the very numerous workers crippled as the result 

 of industrial accidents. H. M. V. 



Our Bookshelf. 



Engrais. Amendements Produits anticrypto- 

 gamiques et Insecticides. Par Dr. E. 

 Demoussy. Pp. xi + 297. Paris and Liege : 

 Ch. Stranger, 1919. Price 15 francs. 

 Dr. Demoussy's manual on the analysis of fer- 

 tilisers is written for the trained chemist; it is 

 founded on the methods laid down in 1897 by the 

 Comite des stations agronomiques, but unofficial 

 methods in use in the principal French laboratories 

 are also described. After a short introduction on 

 the laws regulating the sale of fertilisers, the 

 author deals in the first two chapters with the 

 collection of samples and their qualitative exam- 

 ination. The following four chapters treat of 

 the determination of nitrogen, phosphoric acid, 

 potash, and manganese, the arrangement being 

 according to the substance to be determined, and 

 not the material in which it is found. The 

 methods are for the most part well known in this 

 country, and call for only a few remarks. The 

 longest section is that devoted to nitrogen. The 

 official method for nitrates is that of Schloesing, 

 and no mention is made of the zinc-copper couple, 

 while for organic nitrogen the Kjeldahl and soda- 

 lime processes are both recommended. The latter 

 has fallen into almost complete disuse in this 

 country, and probably few chemists here would 

 agree with the opinion that it is the more econ- 

 omical in time when many samples are to be 

 examined. Where a purely chemical analysis 

 would be of little value, as in the case of dried 

 blood, drawings of the materials as seen under 

 the microscope are given. The value of these 

 would have been greatly increased if the magnifi- 

 cation had been stated. Under the head of potash 

 no reference is made to flue-dust ; in this case the 

 official methods would have to be slightly modified 

 to ensure complete removal of silicic acid. 



The second and third parts of the book deal 

 with materials such as lime and with fungicides 

 and insecticides. Tables for the calculation of 

 results are added, and the appendix contains the 

 French laws and regulations dealing with the sale 

 of fertilisers. 



The book is well arranged and clearly written, 

 and its value is added to by notes on the form 

 in which the various materials are put upon the 

 NO. 2650, VOL. 105] 



market and the adulterations to which they are- 

 liable. It should prove very useful in analytical, 

 laboratories in this country as well as in F"rance. 

 Donald J. Matthews. 



Flora of Jamaica: Containing Descriptions of the 

 Flowering Plants known from the Island. By 

 William Fawcett and Dr. Alfred Barton Rendle. 

 Vol. iv.. Dicotyledons: Families Leguminosae- 

 to Callitrichaceae. Pp. XV-H369. (London: 

 British Museum (Natural History), 1920.) Price 

 255. 

 The fourth volume of this admirable tropical flora 

 has lately appeared, and contains the Dicotyledons 

 from Leguminosae to Callitrichaceae (on the 

 Englerian system). It maintains the high 

 standard of its predecessors, and shows a great 

 advance upon some well-known tropical floras in 

 being illustrated by excellent text figures, and not 

 by a series of separate plates, which are usually 

 troublesome to consult. The index is also con- 

 venient in being only a single list of both scien- 

 tific and popular names and synonyms. Turning 

 to the contents of the book, which have been 

 worked up with much care and after consulta- 

 tion of all the older authors and collections, 

 an interesting feature that may be noticed is the 

 extraordinary generic similarity of the flora to 

 that of other islands, even at immense distances 

 from Jamaica. In the Leguminosae, for example^ 

 the first family in the volume, 118 Jamaica species, 

 or 80 per cent., belong to genera that also occur 

 in Ceylon, 74 per cent, to genera occurring in 

 Formosa, and even in the case of so far distant 

 an island as New Caledonia 63 per cent, of the 

 Jamaica species belong to common genera. It 

 is clear that the islands on the whole contain the 

 older genera, which have been able to reach them. 

 Of the Jamaica genera of Leguminosae 70 per cent, 

 are cosmotropical, and only 14 per cent, are con- 

 fined to the New World. Again, one notices that 

 the proportion of endemic species is small in 

 Leguminosae, and larger in Euphorbiaceae and 

 some of the other families, just as in other floras. 

 It would appear a promising piece of work to 

 make a careful statistical study of numbers and 

 proportions of endemics in many countries, for it 

 evidently follows definite, if perhaps recondite, laws. 



Butter and Cheese. By C. W. Walker Tisdale 

 and Jean Jones. (Pitman's Common Com- 

 modities and Industries.) Pp. ix-Fi42. 

 (London : Sir Isaac Pitman and Sons, Ltd., 

 n.d.) Price 2s. 6d. net. 

 The writers of this book have succeeded in giving 

 to the general reader a very good account of the 

 essential facts in connection with the dairying 

 industry. As was to be expected, it was neces- 

 sary to treat the subject on what are generally 

 termed popular lines, but certain of the chapters 

 are written in a particularly clear manner and 

 with full regard to the essential technical points. 

 Not only the chief branches of the dairy industry 

 — cheese-making and butter-making — are dealt 

 with, but also the production of milk, the methods 

 of analysis, and the judging of dairy produce are 



